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Apollo-15: lunar geology at new heights

Anatoly Zak, Spaceflight Correspondent
Apr 9, 2016, 21:15 UTC

Sen—For the fifth expedition to the Moon, NASA rolled out a beefed up version of the Apollo-Saturn-5 complex, known as J series. Thanks to various changes and improvements to the launch vehicle, the spacecraft and the flight profile, the typical duration of the lunar expedition was extended from 8-10 days to 12 days and the stays on the lunar surface were doubled in length from 1.5 days to nearly three days. The total duration of spacewalks on the lunar surface was increased to 20 hours.

The upgraded lunar module was equipped with a foldable electric rover developed by Boeing. More flexible spacesuits with more capable life-support backpacks were also introduced.

In addition, new scientific gear was squeezed into the service module of the Apollo spacecraft for studies of the Moon from lunar orbit. In total, the Apollo spacecraft gained 2.4 tons in mass, reaching 46.8 tons.

Thanks to experience and the new capabilities, NASA felt comfortable to dispatch the first expedition of the J series to a more difficult but geologically more interesting mountainous terrain on the Moon near Apennine Mountains and Hadley Rille.

The Apollo-15 mission lifted off from Cape Canaveral on July 26, 1971, at 09:35 a.m. local time. Onboard were commander David Scott, Command Module Pilot Alfred Worden and Lunar Module Pilot James Irwin.

On July 30, after some trouble with the docking mechanism, the Falcon lunar module with Scott and Irwin onboard separated from the Endeavour command module piloted by Worden.

Falcon's risky and steeper-than-usual descent among mountains ended with a rough landing on the very edge of a small crater leaving the lunar module in a precarious and tilted position with only three out of four legs sitting on the surface. At the same time, the nozzle of the descent engine ended up plowing into the dust. Fortunately, the engine was shut down just in time and the nozzle served as an extra support on the uneven surface.

After a short peek at the surrounding landscape through the top hatch of the module and a period of sleep, the pair of astronauts made their first sortie on the lunar surface on July 31. Obviously, the first order of business, after checking their tilted craft, was to unpack and power up the rover. Some 40 minutes later the astronauts began the first drive on the Moon. They accelerated to a speed of up to 10 kilometers per hour, but their distance was limited to ensure they could walk back to the lunar module in case of car trouble. Still they had chance to come to the very edge of the Hadley Rille, which snaked the area for many miles and enjoy the spectacular view.

The advantage of the rover became obvious right away—in the first trip they drove as far as 4.8 kilometers from the module.

After getting back to the Falcon, the astronauts installed an already routine set of ALSEP scientific experiments. They also had the task of making a pair drills up to three meters deep but were able to penetrate the rocky soil only to around 1.7 meters by the time when their six-hour, 33 minute spacewalk was over.

The drilling effort was resumed during the next spacewalk, a day later, but not before some potentially dangerous maintenance work on a water leak in the cabin, which, fortunately, did not cause any short circuits.

Despite another struggle with drilling, the astronauts still spared enough time to make an adventurous car ride across the lunar landscape. The second sortie on the lunar surface lasted seven hours 12 minutes.

With many of the tasks out of the way, the third sortie on August 2 became the shortest one, logging four hours 50 minutes. As before, it included a scenic car ride. The astronauts also marked a stamped letter as having been posted to the Moon, proved the truth of Galileo's law to all skeptics by dropping a feather and a hammer in front of the camera and left a small plaque on the surface with the names of 14 fallen space travelers.

At the conclusion of the spacewalk, the astronauts parked their rover around 100 meters from the lunar module, so that its camera could document the blastoff from the Moon.

In total, Scott and Irwin spent nearly 67 hours on the Moon, returning with 77 kilograms of priceless lunar artifacts, including a sample from the three-meter drill.

After docking with the command module, the joint crew remained in the lunar orbit for another two days for a series of experiments and studies.

On August 4, the astronauts released a small scientific satellite from the service module into lunar orbit and around one hour later, Apollo-15 propelled itself toward Earth. Next day, the crew depressurized the cabin, and Worden made a short spacewalk from the command module to the service module where he removed exposed film from the camera and brought it into the cabin for the return to Earth.

The command module successfully landed in the Pacific Ocean on Aug. 7, 1971, at 20:45 UTC, not far from USS Okinawa. During the descent, one parachute failed, but two others ensured a safe splashdown. To the relief of the crew, the exhaustive post-flight quarantine was abandoned in the runup to their launch.

The mission of Apollo-15 lasted 12 days and seven hours. Unfortunately, the increasingly scientific nature of the Apollo program made it a victim of its own success: The general public and politicians had trouble absorbing and appreciating more and more complex details of the continuous lunar exploration.